Periodic wave generator



2 m43 H. A. WHEELER PERIODIC WAVE GENERATOR Filed March 29, 1939INVENTOR H ROLD A. WHEELER Bf ATTORNEY ?atented Dec. 2, 1941 orifice 1ramonrc WAVE GENERATOR Harold A. Wheeler, Great Neck,; N. Y., assignortov Hazeltine Corporation, a corporation of Dela- Wall'e ApplicationMarch 29, 193s, semina. 264,716

` (ci. 25o-36) 10 Claims.

This invention relates to periodic wave gen: erators and, while ofgeneral application, it. is especially useful in the development ofscanning elds of saw-tooth wave form for use in television systems.

Periodic waves having complexpwa've forms, such as saw-tooth and relatedforms, are useful for various purposes. In television systems, forexample, at both the transmitter and the receiver, electrostatic orelectromagnetic fields of sawtooth Wave form are utilized in scanningsystems to deflect a beam focused on a target, such as the cathode rayin a cathode-ray tube system, so as to cause the beam to scan successivefields or series of parallel lines on the target. Theseelds are producedby applying periodic current or voltage waves of the desired wave formto field-l producing elements.

In general, it is required that periodic wave generators of the typedescribed be capable of developing waves of precisely the desired waveform; in a television system, of a form suitable to eect accuratelyuniform velocity of trace and rapid retrace of the scanningV beam, thatis, a saw-tooth wave comprising a linear trace stroke and a retracestroke of only a fraction offthe duration of trace stroke.' Furthercharacteristics generator includes a lfeed-back circuit for the tuberesponsive to operating conditions in the output circuit for effectingoperation of the tube over the aforesaid part of its operating range andone of the limiting regions and for causing the tube to develop in theoutput circuit a current wave including both saw-tooth and pulsecomponents. The generator additionally n-g' cludes means connected incircuit and cooperatessential to such generators are simplicityofconstruction and dependability inv operation.

It is an object of the present invention, therefore, to provide animproved generator for developing a periodic wave of complex wave form,such as a saw-tooth or related form, which may be either a current wavefor electromagnetic scanning or a voltage wave for electrostaticscanning.

It is a further object of the invention to pro.-

vide a periodic wave generator having one or more of the desirablecharacteristics and features referred to above.

In accordance with the present invention, a

Ygenerator of periodic saw-tooth waves having means from the supplycircuit by substantially.

constant current in one direction during the trace periods anddischarging of the capacitance v means by current in the oppositedirection during retrace periods. The vacuum tube has a gridvoltage-conductance characteristic free from excessive curvature over apart of its operating range between limiting regions thereof.' The ingwith the capacitance means for dividing the aforesaid current in twopaths, one of the paths including the capacitance means. The impedancesof the aforesaid paths are relatively so proportioned that there flowsthrough the capacitance means only the one of the aforesaid currentcomponents required `to produce the desired saw-tooth wave therein withthe tube. operating only over the aforesaid part of its operating rangeduring trace periods. a .5'

For a better understanding of the invention,

together with other and furtherv objects thereof, reference is had tothe following description taken in connection with the accompanyingdrawing and its scope will be pointed out in the appended claims.

\ In the accompanying drawing, Fig. 1 is a circuit diagram of a periodicwave generator em-A .bodying the present invention; Fig. 2 is a circuitvdiagram of a modified form of the output circuit of the generator ofFig. 1; Figs'. 3 and 4 are circuit diagrams of modified forms ofperiodic wave generators embodying the invention: while Fig. 5 is agroup of curves illustrating thel wave forms o f various currents andvoltages developed in the generator of Fig. 1.

Referring now more particularly to Fig. 1 of the drawing, the generatorillustrated comprises an energy-storage means, such as an inductanceelement t0, which may be a magnetic scanning element of a televisionscanning system, through which it vis desired to produce acurrent ofsawtooth wave form. The inductance element I0 is included in the outputcircuit of the generator in series with a resistor H, which maycomprise, in.V whole or in part, the inherent resistance of theinductance element, a blocking condenser I2, a' j source of operatingvoltage, such as a' battery I3, and a repeater device, preferably avacuum tube I4 which may be a triode, as shown, or a multi-- grid tube.For the purpose of controlling certain operating conditions of thesystem in accordance with the present invention and for applying theoperating potential from battery I3 to the anode of the tube I4, aresistor I5' is connected Ain parallel with the series-connected inoi!lresistors I8 and ila lso that only'a' ductance-element Il. resistor II,and condenser I2. Since the resistor I l carries the space current oftube i4, it must be limited to a fairly small resistance value 'and anlinductancey element l may be included in seriesy therewith, asl

' shown, although, in some cases, this element may be omitted. y n

For the purpose of controlling the tube Il, there is provided arfeed-back system responsive 'f to operating conditions in the outputcircuit of the generator and comprising a reversing and limiting vacuumtube I6 whichmay be a triode, as shown, or a multigrid tube. The inputcir-v cuit of the tube I8 is coupled to the loadcircuit of tube Il byway oi' a coupling impedance in'- cluding a series-connected condenserI1 and voltage-divider resistors I8, Ita, and lsb, the control grid oftube I6 being connected at the Junction portion of the availablefeed-back `voltage -is applied to the tube It. yThe condenser I1 servesto absorb saw-tooth wave-form components from the feedn back voltage sothat only pulse components.

' thereof are appliedto the'tube I8. Tube I6 is arranged to operatebeyond both its upper and lower cutoff limits so asltol derive .inl itsload 'circuit,presently to be described,A a voltage o! lthe lrequiredwave form and'amplitude properly to stabilize the operation of thesystem. Positive i synchronizing pulses for the generator may bel 1applied to the potential may be supplied from a suitable source. forexample, ya battery 23, by way lof a resistor 2| and the load resistor2|. The load circuit 2|', 22 iscoupled to the control grid of the tubeIl by way oia suitable condenser 25 and gridleak resistor 2i. Anegative-bias potential is applied to the control grid of the tube Il byway of the resistor from a suitable source, for example, battery 21.While. for simplification, batteries have been illustrated as sources ofdirect current and bias-voltage supply, it will be understood that, inpractice, conventional power supply circuits will ordinarily beutilized.

'I'he operation of the generator of Fig. 1 may best be understood byfirst neglecting the resistor I5 and the major Apart of the resistor 2|,which comprise essential parts of the present invention, and assumingthe former to be replaced by a large choke to carry the space currentoi.' tube Il. During the trace period of each cycle, the tube I8 isbiased below grid-bias cutoi! and the condenser 22 is charged throughthe resistor. 24 causing the potential of the upper terminal of thecondenser 22, which potential is applied to the control grid of the tubeIl, to beco e increasingly positive so that vcurrent bui s up throughthe series circuit including the tube I4 and inductance element I0.'This current continues to rise until the operating conditions aredisturbed, for example, by the application of a positive synchronizingpulse to the tube I6, which initiates the retrace portion of the cycle.Buchl pulse causes the potential of the control grid of the tube Il toincrease negatively, reducing itsoutput current. This reduction incurrent is reas just described, so

voltage of the required waveyform.- Operating' y cluding tube I6.

f ates not only over oi'. its characteristic 'but also over 1 the lowerygenerated by means of the feed-back circuit in- As long as the currentin the tube Il continues to fall, a positive voltage is fed back tor thetube I6.A The tube 'I4l is thus. regenerated to cutoiif. As soon as thecurrent in the tube Il' is interrupted, the positive feed-backvoltagefis removed from'thetube I6 and it returns to cutoff. The traceperiod described above is then repeated to initiate the next cycle. f

While the grid voltage-conductance characteristic cfa repeater, such asthe is substantially linear over the intermediate portion of its range,or at least does not have excessive curvature, the limiting or upper andlower Lcutoff! regions oi' the range are sharply curved.

The synchronizing signal determines the termination of the trace periodsand, hence, the upper limit of the operating range. The'circuit con-lstants are preferably so related to the period of the synchronizingsignal thatl this upper limit is just within the linear portion o! thetube charfacteristic. However, with the system operating, lthat thecurrent through the tube Il is reduced to zero'at the lend loftheretrace period, it will be seen that the tube operthe usefullintermediate portion sharply curved limiting region in the early partlof the trace period. l

In accordance with 'the present invention, however, there are providedmeans for shifting the operation of the device substantially away fromthis lower limiting-regionduring the entire. trace period. This is accurrent component complished by causing a pulseto be superimposed on thedesired saw-tooth current'component in the generator output circuit. Forthis purpose the resistor 2|., included in the load circuit of the tubeIl, is given a substantial valuel so thatl there isl developed 'acrossthis circuit and applied to the f control grid of the' tube Il acomposite control voltage wave including not only' the saw-tooth -wavecomponent developed across condenser 22 but also a pulse componentdeveloped across the resistor 2| which is of a value greater than neededfor the development of saw-tooth current in the tube I4. Since it isnecessary that only the saw-tooth current component passes through theinductance element ||I.1the`resistor Il is connected in paralleltherewith andiso proportioned relative thereto that it eiiectivelyby-passes all of the pulse-current component and, incidentally, part ofthe saw-tooth current component.

rlihe actual operation of the system, therefore, 'is modiiied withrespect to that described above. In Fig. 5 curves A-D, inclusive,illustrate voltages and currents developed at various points inthesystem during the actual operation thereof.

Thus, curve A illustrates the desired saw-tooth saw-tooth currenttherethrough so that the total voltage developed across the load circuitof tube Il by the saw-toothload current is of the combined saw-tooth andpulse wave form illustrated by curve C. The current through the resistorI5, therefore, and inductance 0, where such is ncluded in the circuit,is also of saw-tooth and pulse wave form. yThe total current which mustbe passed by the tube I4, therefore, is oi' the wave form illustrated bycurve D, having both pulse n and saw-toothloomponents. Current of thisrevacuum tube Il,

veloped thereby and applied to the control grid of the tube I4. The endof the trace period, as explained above, is determined below the upperlimiting region bythe application of the synchronizing pulse to thegenerator. During the retrace period the combined pulse and saw-toothretrace components carry the tube through the lower limiting regionoiits repeating lcharacteristic to cutoiI and the tube thereupon swingsaway from this lower limiting region so that the trace period begins inand extends over the intermediate part of the range of thecharacteristic which is free from excessive curvature.

In certain casesit may be necessary for the resistor I to be of arelatively low value in order properly to carry the direct current. Insuch a case. in the absence of the inductance 9, the

path including resistor I5 would take an excessive amount of the pulsecurrent. 'I'he inductance 8, however, may be included, as shown, for thepurpose of providing greater impedance to the pulse current when theresistor is of such low value.

It will be appreciated that the grid voltageconductance characteristicof the tube I4 tends to cause curvature of the saw-tooth wave form ofthe current developed by the-system during the trace period. Likewise,certain impedance elements in the system tend to cause such a curvature;for example, the condenser I2, to'- gether with the other load circuitelements connected therewith, the resistor 28 and condenser 25, and theresistor 24 anl condenser 22. 'I'he curvature which these impedanceelements tend to cause, however, is opposite to that due to the tube Iland the circuit constants are so proportioned that these Oppositecurvature eilects compensate each other. Thus, while the condenser I2has so large a capacitance that it does not greatly affect the wave formoi' the wave developed by the system, any curvature eilected thereby isgalanced against the characteristic of the ubeI While a voltage oi' bothpulse and saw-toothl wave-form components is impressed upon thefeed-back circuit, the saw-tooth components are absorbed, as explainedabove, by the condenser I1 and only the pulse components are applied tothe input circuit oi' tube I8. Tube II being operated beyond both itsupper and lower cutofl' limits, a pure pulse current is developedthereby4 and the control voltage oi' the required complex wave form isdeveloped across its load circuit comprising resistor 2| and condenser22.v Not only does the limiting action of the tube I8 properly limit theamplitude of the control wave but it serves also to avoid cumulativewave-form distortion and thus stabilizes thewave form and amplitude ofthe wave developed by the system.

In order that the tube Il may simultaneously supply puresaw-toothfeurrentntoftheload inductance l0 and a pulse andsaw-'tooth'current inresistor I5, the time constant of the couplingimpedance 2l, 22 is made equal to that of the output circuit as follows:

in which C, R, and L are the capacitance, resistance, and inductance,respectively, ot the particular elements indicated by the appendednumerals. Ihis relation is based on the assumption oi' a linear gridvoltage-conductance characteristic in the tube I4 which is approximatelyrealized v over the major portion of its operating range.

In order to procure a pure pulse voltage across the resistors I la andI8b, the condenser Il is proportioned, 'as explained, to absorb thesaw-tooth voltage developed across the resistor Il in the output circuitas follows:

CHRF

in which, as in Equation 1, C, R, and L are the4 and beginning of theretrace period; the remain` ing characteristic of the wave, the durationoi' the retrace period, is determined by the tube Il reaching cutoil',whereupon the tube I4 is instantaneously swung away from the cutofi'region to begin the trace period.

It will be seen that, in accordance with one aspect of the presentinvention, impedance means, in the system of Fig. 1 the resistor I5,effeetively is connected in parallel and cooperates with theenergy-storage means to divide the current through the output circuitinto two paths. One of the paths includes the energy-storage means, theinductance element lli in Fig. 1, while the other path includes theimpedance means 9, I5. The paths are so proportioned that there ilowsthrough the energy-storage means only the current components required toproduce the desired saw-tooth wave which, in the generator of Fig. 1, isthe current o! saw-tooth wave form.

In Figs. 2, 3, and 4, there are illustrated modications of theinvention. Like reference numerals indicate corresponding parts inFigs.' 1 4, inclusive.

In Fig. 2 there is illustrated a modified form of output circuit whichmay' be;4 substituted for the corresponding circuit in the generator ofFig. l. In the circuit of F1g.2. a resistor Iia is connected directlyacross the inductance element III andresistor II and an inductanceelement or choke 28, of the iron-core type, is connected in parallelwith the circuit with its lower terminal at the inner side of condenserI2, providing a separate direct-current path for the space current o!the tube I4. Since, with this arrangement, the shunt resistor I 5a doesnotl carry the space current of the tube I4, with resultant voltagedrop, as in the case of the resistor I5 of Fig. l, the resistor Ia. maybe made any size desired without aecting the space current or anodevoltage of tube Il and required battery voltage is less. c

In Fig. 3 a modiiled iorm of the generator of Fig. l is shown' whichincludes certain additional advantageous features whereby variousoperating characteristics. of the system may be readily adjusted.Except, as explained below, the generator of Fig. 3 is of the sameconstruction as that of Fig. 1. In the generator oi' 3 a single batteryI3a is provided for supplying the operating potentials oi' both oi' thetubes Il and I 8, these potentials being applied by way of anadjustabletube I6 by way of resistors 24 and 2Ia,

. plitude which is connected to the anode of the latter preferably beingadjustable, as shown. Resistor 34 is connected tothe 4anode of tube I4by way of resistor I5. A voltage-divider resistor is connected acrossbattery |30. and resistor 34 and has an adjustable tap to which theresistor II is connected. The condenser I2 in this case is connecteddirectly between the lower end of resistor II and the cathode of tubeI4. A biasing resistor 36 is included in the cathode circuit of tube I4and an adjustable biasing resistor 31, by-passed by a condenser 38, isincluded in the cathode circuit of tube I6. Condenser 22' may resistor34 be alternatively connected directly to the cathode of tube I6,instead of to ground. This alternative connection 'has the advantage ofreturning the pulse of output current of tube I6 directly to the cathodeandV thereby reducing the requirements ofthe by-pass condenser 38. Thegrid-leak resistor 26a of tube I4 is also adjustable.

The operation of this generator is substantially the same as that of thegenerator of Fig. 1. Here, however, the various adjustable resistorsprovide means whereby the various operating characteristics of thegenerator may be readily adjusted. By adjustment of the resistor 34, theamplitude of the wave developed-by the system may be readily controlled.When increased voltage is applied 4to the ytube I4 for developing a waveof greater amplitude, an increased control voltage is required to -bedeveloped by the tube I6 so that its operating voltage should also beAincreased. The resistor 34 thus provides a single means which may beadjusted simultaneously to effect the proper adjustments of theoperating voltages of both tubes. 4 l

By adjustment of the tap on the voltagedivider resistor 35, the value ofthe direct-current component which flows through the inductance I0 maybe readily controlled. Where the element I0 constitutes a scanningelement of a cathode-ray tube, therefore, this adjustment is useful forvthe purpose of centering the scanning pattern on the target of thetube. Adjustment of the resistor 2 la serves to control the arnplitudeof the pulse component'of the control wave developed by the feed-backsystem. This provides a means for accurately controlling the curvatureof the wave developed by the generator at the beginning of itsv traceperiod. A further control of the linearity or curvature of the wavedeveloped by the generator is provided by the adjustable resistor 26a.Thus, the adjustable resistor 34 comprises means for adjusting the amofthe Wave developed by the generator, the amplitude adjustment beingindependent of the linearity and frequency of the developed wave, andthe adjustable resistors Zia and 23a comprise means for adjusting thelinearity of the ywave developed by the generator, the linearityadjustment being independent of the amplitude and frequency of thedeveloped wave.

The free oscillating frequency of the generator of Fig. 3 is regulatedby the time constant of resistor 31 and condenser 38, which determinesthe end of the trace period'in the absence of a synchronizing pulse. Asstated above, the end of the trace period is determined by the startingof current in tube I6. The operation of tube I6 inFig. 3 is determinedpartly by resistor 31; that is, each pulse of current develops a biasacross the condenser leaks off through the resistor 31 during the trace38 which is applied positively to the cathode of tube I6, and this biaspartially period. As it leaks oir, it reaches a point where currentstarts to now in tube I3, even inthe absence of a synchronizing pulse,whereupon the trace period is ended and retrace begins; that is, asaw-tooth control voltage is ldeveloped across the circuit 31, 38. 'I'hetime constant of resistor 31 and condenser 38 is adjusted so thatI thefree oscillation period is slightly longer than the synchronizingperiod, so that the failure of a single synchronizing pulse will notresult in too great a disturbance of the normal periodicity of thegenerator. Thus, the resistor 31 and condenser 38 comprise means foradjusting the free oscillating frequency of the generator, .thefrequency adjustment being independent of the amplitude and linearity-ofthe developed Wave.

The circuit constants of `a generator such as illustrated in Fig. 3which have proved highly satisfactory in actual practice are as follows:

For improved linearity of trace, the following valuesmay be used inplace of those above:

Resistor 31= 2,700 ohms Resistor 2|=7,000 ohms Resistor 36=800 ohmsResistor ISL- 1,500 ohms Condenser 38:1 microfarad Condenser 25:0.25microfarad Condenser I 2:8 microfarads ator, an important advantage isobtained, since at such low frequencies effective inductance coils aregenerally large and expensive.

In Fig. 4 there is illustrated still another modied form of thegenerator of the present invention which is designed to develop asaw-tooth voltage wave across capacitance means. The generator of Fig. 4is similar to that oi Fig. l except for the output circuit and certaindetails of the circuits of tubes I4 and I8. Here the energystorage meanscomprises capacitance means including series-connected condensers 48,46, grounded at their junction, and a condenser Ilia in parallelVtherewith which may be the deilecting plates of a television cathode-raytube, providing a balanced output circuit. For building up a saw-toothvoltage from a saw-tooth current,

resistors 40, 40 are connected across the con-V densers 46, 46 and Illaand their junction is grounded by way of a battery |3b. The uncommonterminals of resistors 40 are connected across the tube I4 .by way ofcoupling condensers 4|, 4|, anode resistor 42, a. biasing resistor 43,and by-pass condenser 44 included in the cathode circuit of the tube.Anod'e potential is supplied to the tube I4 from a suitable tap onthebattery I3b by Way of a choke 45 and the resistor 42, and thedirect-current path of the battery is completed by a similar choke 45aconnected between the negative or grounded terminal of the battery andthe cathode resistor 43. Chokes 45 and 45a are preferably of the sameinductance and may be wound on the same core.V

Balancingcondensers 46 are eiective *tol bypass pulse-current componentsin the output circuit to supplement the capacitance IIla.

Anode potentialxfor the tube I6 is supplied from the battery I3b by wayof a series resistor 41, by-pass condenser 48, and the resistors 24 and2|. A self-biasing resistor 49 and by-pass condenser 5I) are included inthe cathode circuit of the tube I6 and the lower terminals of theseelements and the input circuit resistor I8b are grounded, by way of thecommon low potential lead of the system and the choke 45a. For the Ypurpose of applying synchronizing pulses to the tube I6, there isprovided an input transformer 5I having its secondary Winding conmc'ctedacross the resistor |817, the terminals 20a, 20a of its primary windingbeing suitable for receiving the synchronizing wave.

1n the generator of Fig. 4, as in Fig. l, the Various circuit elementsare proportioned, so that the characteristic curvature of the tube I4and that of the circuit elements, which tend to cause curvature of thesaw-tooth wave developed by the system, effectively counteract eachother during the trace period. Here the condensers 4| and inductanceelements 45 and 45a are included in the group of elements whose valuesare proportioned for this purpose.

The operation of the generator of Fig. 4 is similar to that of Fig. 1except that here a balanced voltage of saw-tooth wave form is requiredto be developed across the capacitance means instead of a current ofsaw-tooth wave form through an inductanoe element. A pulse voltagecomponent the current ows, and second,` the path provided by resistors40 throughwhich the saw-tooth current flows. That is, the battery I3band the tube f I4 comprise means including a voltage supply wise beexcessive at low frequencies.

, circuit and a vacuum tube for effecting periodic charging of thecapacitance means from the supply circuit by substantially constantcurrent in one direction during the trace periods and discharging oflthe capacitance means by current `flow in the opposite direction duringthe retrace periods. Negligible current flows through the coils 45, 45aand the resistor 41, except for the direct-current components.Negligible voltage :is developed across condensers 4|, 4|. This divisionof current is inevitable since a saw-tooth Voltage is produced acrossthe condenser Illa, and, therefore, across resistors 46 and condensers46.. In this case, the energy-storage means is not only the condenserIlla of the useful load circuit but also the condensers 46, 46, which4are added for the practical reason of 'reducing theimpedance of theoutput circuit, which would othermary, it will be seen that thearrangement of Fig. 4 comprises a generator of periodic sawl tooth waveshaving substantially linear trace and vrelatively short retrace periods.The vacuum tube I4 of the Fig. 4 arrangement has, like the correspondingvacuum tube I4 of the Fig. 1 arrangement, a grid voltage-conductancecharacteristic free from excessive curvature over a part of itsoperating range between limiting regions thereof. Reversing vacuum tubeI6 and the circuit elements I'I, I8, I8a, I8b, 2|, 22 and 24 compriseY afeed-back circuit for Athe vacuum tube I4 responsive to operatingconditions in the output circuit of the latter tube for effectingoperation of the vacuum tube I4 over the curvature-free portion of itsoperating range and one of the limiting regions thereof and for causingthis vacuum tube to develop in its output circuit a current waveincluding both saw-tooth and pulse components.

l, voltage of vacuum tube I4 a feed-back voltage is also required forthe feed-back circuit, as in the circuit of Fig. l. Therefore, aresultant voltage of saw-tooth and pulse wave form must be developedacross the output circuit of the generator. The desired saw-toothvoltage appears across the capacitance means "Illa and current of due tothe flow of current therethrough, the required Afeedback pulse voltagecomponent, since otherwise there would be only the desired sawtoothvoltage across the output circuit.

Thus, in the generator of Fig. 4, it will be apparent that means areprovided whereby the output current is divided between two paths, iirst,the capacitive path including condensers I 0a and 46, 46, through whichthe pulse component of having saw-tooth and pulse wave-form componentsof relative amplitudes independent of those of the aforesaid outputvoltage. The-resistors 40, 4I! comprise means connected in circuit andcooperating with the capacitance means Illa for dividing the current inthe output of vacuum tube I4 into two paths, one of which paths includesthe capacitance means 10a, and the impedance of the paths are relativelyso proportioned that there Hows through the capacitance means Illa onlythe one of the current components required to produce the desiredsaw-tooth wave therein with the vacuum tube I4 operating only over thecurvature-free portion of its operating range during trace periods.

While there has been described what is at present considered to be thepreferred embodiment of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein Without departing from the invention, and it is, therefore,aimed in the appended claims to cover all such changes and modificationsas fall within the true spirit and scope of the invention.

What is claimed is:

l. A generator of periodic saw-tooth waves having substantially lineartrace and relatively cuit including capacitance means, means including avoltage supply circuit and a vacuum tube for effecting periodic chargingof said capacitance` means from said supply circuit by substantiallyconstant current in one direction during said trace periods anddischarging of said capacitance means by current in the oppositedirection during said retrace periods, said vacuum tube having a gridvoltage-conductancer characteristic free from excessive curvature over apart of its operating range between limiting regions thereof, afeed-back circuit for said tube responsive to cperating conditions insaid output circuit for effecting operation of said tube over said partof said range and one of said limiting regions and for causing said tubeto develop in said output circuit a current wave including bothsaw-tooth and pulse components, and means connected in circuit andcooperating with said capacitance means for dividing said current in twopaths, one of said paths including said capacitance means, and theimpedances of said paths being relatively so proportioned that thereflows through said capacitance means only the one of said currentcomponents required to produce the desired sawtooth wave therein withsaid tube operating only over said part of said range during traceperiods.

2. A generator of periodic saw-tooth waves having substantially lineartrace and relatively short retrace periods comprising, an output circuitincluding capacitance means, means including a voltage supply circuitand a vacuum tube for effecting periodic charging of said capacitancemeans from said supply circuit by substantially constant current in onedirection during said trace periods and discharging of said capacitancemeans by current flow in the opposite direction during said retraceperiods, said vacuum tube having a. desired grid voltage-conductancecharacteristic free from excessive curvature over a part of itsoperating range between relatively sharply curved limiting regionsthereof, a feedback circuit for said tube responsive to operatingconditions in said output circuit for controlling said tube to causeoperation thereof over said part of said range and at least one of saidlimiting regions, and means including resistance means eiectivelycoupled to said capacitance means and so proportioned with respectthereto as to shift the operation of said tube substantially away fromsaid limiting region during trace periods.

3. A generator of periodic saw-tooth Waves having substantially lineartrace and relatively short retrace periods comprising, an output circuitincluding capacitance means, means including a current supply circuitand a vacuum tube for eiecting periodic iiow of substantially constantcurrent in one direction through said capacitance means from said supplycircuit during said trace periods, said vacuum tube having a gridvoltage-conductance characteristic free from excessive curvature over apart of its operating range between limiting regions thereof, afeed-back circuit for said tube responsive to operating conditions insaid output circuit for effecting operation of said tube over said partof said range and one of said hunting regions to cause in said outputcircuit a current wave including both saw-tooth and pulse components,l

and means connected in circuit and cooperating with said capacitancemeans for dividing said current in two paths, one of said pathsincluding said capacitance means and the other of said paths includingresistance means and said paths being so proportioned that there nowsthrough said one path only said current components of pulse wave formwith said tube operating over said part of its range during traceperiods.

4. A generator of periodic saw-tooth waves having substantially lineartrace and relatively short retrace periods comprising, an output circuitincluding capacitance means, means including an energy supply circuitand a vacuum-tube repeater having a control electrode for effectingperiodic flow of substantially constant current through said capacitancemeans during said trace periods, said vacuum-tube repeater having a gridvoltage-conductance characteristic free from excessive curvature over apart of its operating range within upper and lower limiting regions, afeed-back circuit for said tube comprising a reversing tube having aninput circuit-and impedance means coupling said input circuit to saidoutput circuit and proportioned to derive therefrom a feed-back voltageof pulse wave form, and a load circuit for said reversing tube coupledto said vacuum-tube control electrode comprising a series-connectedresistor and condenser proportioned to develop a control voltage wavehaving saw-tooth and pulse wave form. components for causing operationof said repeater tube over said part of saidrange and said lowerlimiting region, and means cooperating with said capacitance means forshifting the operation of said tube substantially away from said lowerlimiting region substantially simultaneously with the initiation of saidtrace periods.

5. A generator of periodic saw-tooth current waves having substantiallylinear trace and relatively short retrace periods comprising, an outputcircuit including an impedance element, a current supply circuit and arepeater vacuum tube for effecting periodic flow of current through saidoutput circuit and developing voltage thereacross, said tube having agrid voltageconductance characteristic free from excessive curvatureover a part of its operating range within relatively sharply curvedupper and lower limiting regions, a feed-back circuit for said repeatertube comprising a reversing tube and a complex impedance proportioned toderive from said output voltage a feed-back voltage having saw-tooth andpulse wave-form components of relative amplitudes independent of thoseof said output voltage for effecting operation of said repeater tubeover said part of said range and said lower limiting region duringretrace periods of operation. means for determining the duration oftrace periods of operation of said repeater tube and limiting saidoperation below said upper limiting region, and impedance means inparallel withl said impedance element for by-passing the pulsecomponents of the current from said impedance ele-` ment thereof toshift the operation of said repeater tube substantially above said lowerlimiting range substantially simultaneously with the initiations of saidtrace periods.

6. A generator of periodic saw-tooth waves having substantially lineartrace and relatively short retrace periods comprising, an output circuitincluding capacitance means, a voltage supply circuit and a vacuum-tuberepeater for eifecting periodic charging and discharging of saidcapacitance means and developing a voltage across said output circuitfrom said supply circuit during said trace and retrace periods, saidtube having a grid voltage-conductance characteristic tree fromexcessive curvature over a to said output circuit and part of itsoperating range within upper and lower limiting regions, a feed-backcircuit for said repeater tube comprising a reversing tube and a compleximpedance proportioned to derive from said output voltage a feed-backvoltage having saw-tooth and pulse wave-form components of relativeamplitudes independentcf those of said output voltage for effectingoperation of said repeater tube over said part of said range and saidlower limiting region during retrace periods of operation, means fordetermining the duration of trace periods of operation of said repeatertube and limiting said operation below said upper limiting region, andresistance means in parallel with said first-mentioned capacitance meansfor by-passing said saw-tooth wave-form current components from saidcapacitance means to shift the operation of said repeater tubesubstantially away from said lower limiting region substantiallysimultaneously with the initiation of said trace periods, whereby theoperation of said tube is held above and below said lower and upperlimiting regions, respectively, during said trace periods. Y

7. A generator of periodic saw-tooth waves having substantially lineartrace and relatively short retrace periods comprising, an output circuitincluding capacitance means, means including a voltage supply circuitand a vacuum-tube repeater having a control electrode for effectingperiodic charging of said capacitance means from said supply circuit bysubstantially constant current in one direction during said traceperiods and discharging of said capacitance means by current flow in theopposite direction during said retrace periods, said vacuum tube havinga grid voltage-conductance characteristic free from excessive curvatureover a part of its operating lrange within upper and lower limitingregions, a feed-back circuit for-said repeater tube comprising areversing tube having an input circuit and impedance means coupling saidinput circuit proportioned to derive therefrom a feed-back voltage ofpulse wave form and a load circuit for said reversing tube coupled tosaid repeater tube control electrode and comprising a series resistorand condenser for developing a control voltage wave having saw-toothwave-form components and pulse Wave-form components determining theduration of retrace periods of operation and to effect operation of saidrepeater tube within one of said limiting regions during said retraceperiods, means for applying synchronizing pulses to said input circuitfor determining the duration of trace periods of operation of saidrepeater tube within said part of said range, and resistance means inparallel with said first-mentioned capacitance means for by-passing saidsaw-tooth wave-form current components from said capacitance means toshift the operation of said repeater tube substantially away from saidlast-mentioned limiting region substantially simultaneously with theinitiation of said trace periods, whereby the operation of said tube isheld above and below said lower and upper limiting regions,respectively, during said trace periods.

8. A generator of periodic saw-tooth Waves having substantially lineartrace and relatively short retrace periods comprising, an output circuitincluding energy-storage means, an energy supply circuit, and a repeaterdevice for effecting periodic charging and discharging of said storagemeans from said supply circuit, said device having a repeatingcharacteristic free from excessive curvature over a part of itsoperating range between relatively sharply curved limiting regionsthereof, a feed-back circuit for said device responsive to operatingconditions in said output circuit for controlling said device to causeoperation thereof over said part of said range and at least one of saidlimiting regions, impedance means effectively coupled to said storagemeans and so proportioned with respect to the impedance thereof as toshift the operation of said device substantially away from vsaidlimiting region during trace periods, means for adjusting the amplitudeof the wave developed by said generator, said amplitude adjustment beinginde-` pendent of the linearity of said developed wave,

and means for adjusting the linearity of the wave 1 developed by saidgenerator, said linearity adjustment being independent of the amplitudeof said developed wave. f

9. A generator of periodic saw-tooth waves having substantially lineartrace and relatively short retrace periods comprising, an output circuitincluding energy-storage means, an energy supply circuit, and a repeaterdevice for effecting periodic charging and discharging of said storagemeans from said supply circuit, said device havy ing a repeatingcharacteristic free from excessive curvature over a part of itsoperating range between relatively sharply curved limiting regionsthereof, a feed-back circuit for said device responsive to operatingconditions in said output circuit for controlling said device to causeoperation thereof over said part of said range and at least one of saidlimiting regions, impedance means effectively coupled to said storagemeans and so proportioned with respect to the impedance thereof as toshift the operation of said device substantially away from said limitingregion during trace periods, means for adjusting the amplitude of thewave developed by said genand means for adjusting the free oscillatingfrequencyA of said generator, said frequency adjustment beingindependent of the amplitude of said developed wave.

10. A generator of periodic saw-tooth waves having substantially lineartrace and relatively short retrace periods comprising, an output circuitincluding energy-storage means, an energy supply circuit, and a repeaterdevice for effecting periodic charging and discharging of said storagemeans from saidsupply circuit, said device having a repeatingcharacteristic free from excessive .curvature over a part of itsoperating range between relatively sharply curved limiting regionsthereof, a feed-back circuit for said device responsive to operating.conditions in said output circuit for controlling said device t0 causeoperation thereof over said part of said range and at least one of saidlimiting regions, impedance means effectively coupled to said storagemeans and so proportioned with respect to the impedance thereof as toshift the operation of said device substantially away from said limitingregion during trace periods, means for adjusting the linearity of thewave developed by said generator, said linearity adjustment beingindependent of the frequency of the developed wave, and means foradjusting the free oscillating frequency of said generator, saidfrequency adjustment being independent of the linearity of saiddeveloped wave.

HAROLD A. WHEELER.

